Poly(aryl ether ketones) are known crystal-line polymers. They offer an exceptional balance of properties; namely high melting point, exceptional thermal stability, excellent hydrolytic stability, high stiffness and strength, good toughness and excellent solvent and environmental stress rupture resistance.
Poly(aryl ether ketones) are known in the art as evidenced by Johnson et al, U.S. Pat. Nos. 4,108,837 and 4,174,175; Dahl, U.S. Pat. No. 3,953,400; Dahl et al U.S. Pat. No. 3,956,240; Dahl, U.S. Pat. No. 4,247,682; Rose et al., U.S. Pat. No. 4,320,224; Maresca U.S. Pat. No. 4,339,568; Attwood et al., Polymer, 1981, vol. 22, August, pp. 1096-1103; Blundell et al., Polymer, 1983 vol. 24, August, pp. 953-958; Attwood et al., Polymer Preprints, 20, no. 1, April, 1979, pp. 191-194; and Rueda et al., Polymer Communications, 1983, vol. 24, September, pp. 258-260.
Thus, poly(aryl ether ketones) are well known; they can be made from a variety of starting materials; and they can be made with different melting temperatures and molecular weights. Nominally, poly(aryl ether ketones) are crystalline and can be made tough, i.e., exhibit high values (&gt;50 ft-lbs/in.sup.2) in the tensile impact test (ASTM D-1822). They have many uses and may be fabricated into any desired shape, e.g., moldings, coatings, films, or fibers.
Poly(aryl ether ketones) prepared from biphenol as a starting monomer have excellent mechanical properties. However, the melting points of such polymers are over 400.degree. C. Such high molecular weight polymers are difficult to prepare due to the high polymerization temperatures required. Further, due to their high melting points, fabrication by conventional polymer fabrication methods is very difficult.
Thus, there is a desire to lower the melting point of the poly(aryl ether ketones) derived from biphenol without substantially affecting the glass transition temperature (Tg) and, thus, the mechanical and crystallization properties.
European Patent Application, Publication No. 0 184 458, published June 11, 1986, describes aromatic polyetherketones containing the repeat units EQU O--Ph--O--Ph--CO--Ph-- (I)
and EQU O--Ph--Ph--O--Ph--CO--Ph (II)
in the relative molar proportions I:II of 95:5 to 60:40, preferably 90:10 to 60:40. It is stated in this publication that the obtained ketone polymer has similar properties to known polyetherketones but has a lower crystalline melting temperature, thus allowing processing at a lower temperature.